The present invention relates to a wireless transmission system. In recent years the wireless LAN standard using the IEEE 802.11 as a standard therefor is utilized globally. A typical method of media access includes an autonomous distributed control system based method such as Distributed Coordination Function (DCF) or Enhanced Distributed Channel Access (EDCA). Meanwhile, in order to assure QoS (Quality of Service) to customers and to provide services for which timeliness is required, centralized control system methods such as Point Coordination Function (PCF) or Hybrid Coordination Function Controller Channel Access (HCCA), or the like, which uses polling signals, are widely used.
JP2012-235453A and JP2005-80162A exist as background art of the present disclosure. JP2012-235453A describes “Selective polling techniques are utilized to selectively poll stations within a wireless network in order to ensure that a station failing to properly transmit data is given an opportunity to rectify the transmission failure. The selective polling techniques can be applied to any polling-based system, thus maintaining backwards compatibility with legacy systems” (Abstract).
JP2005-80162A describes “The radio base station device for exchanging data with a plurality of radio terminal devices is provided with: a means for transmitting a beacon in the period of TB; a means for transmitting data after access control according to a CSMA/CA protocol; a means for transmitting to a radio terminal device a polling signal giving an instruction of down data transmission and up data transmission; a means for transmitting a polling signal to be transmitted to the radio terminal device preferentially over a packet to be transmitted according to the CSMA/CA protocol; and a means for making, when data having a period of a time interval T1 are transmitted or received, the beacon transmission interval TB to be m times of T1 (m is a natural number) and virtually making the time interval T1 to be a slot with a fixed time interval T2 having a relationship of T1=n T2 (n is a natural number)” (Abstract).